After upgrading my kernel to version 4.16 and zfs to version 0.7.9-3 tonight, today I also saw the issue @Teeminus described here. Didn't look in the section "Acces Rights Management - Shared Folders" in the omv webui tonight. So I didn't recognize the issue. I had some problems while updating my system to latest backport kernel and latest zfs tonight. I described the solution here:

Today it was not possible to export my pool anymore, I always got the following message:

Source Code

zpool export mediatank

cannot export 'mediatank': pool is busy

It was also not possible for me to identify which service keeps the pool busy. So, after some friggeling I did the following procedure:

shutdown the server

removed the sas/sata cables of my zfs disks

started the server again

rmmod zfs to unload the zfs modules

rm -R /mediatank/ to remove the mountpoints of my pool

modprobe -a zfs to load the zfs modules

shutdown the server

attached the sas/sata cables of my zfs disks

started the server again

my pool got imported automatically

accessed the sections "Storage - File Systems" and "Storage - ZFS" in the omv webui, looks as expected and seems to work

accessed the section "Acces Rights Management - Shared Folders" in the omv webui, got the yellow line message in the omv webui, that notices about changes and I accepted them

After this procedure I saw my zfs file systems under "Device" back again. I also see my zfs file systems in the dropdown list, if I edit one of my shared folders. If I remember right, before executing the above described procedure, I only saw "NA" or something like this in the "Device" section of the following table:

Did some reboots, a "shutdown -h now", a restart and again some reboots. I think it works now. No issues at the moment. We will see... Maybe this procedure helps somebody else.

EDIT: I think the key is last point of the procedure, the yellow line message, where omv recognized that something has changed and I accepted these changes. By the way... I am not really sure, if the message appeared at this point, or directly when I accessed the omv webui, or at some point between logging into omv webui and accessing the section "Acces Rights Management - Shared Folders".

So the ZFS Plugin was updatet today and erverything works fine with a fresh installed and updatet omv 4.1.7 with 4.16.0.bpo.1. Massive thanks to subzero79 and ryecoaaron for updating the plugin and helping a novice like me

Nice.
I have just updated the plugin here too, and can confirm that I now see ZFS pools in the dropdown. Go to the ZFS tab first and accept the config changes, then to the shared folders - and they are there! Nice work @ryecoaaron and @subzero79

@Blabla Read my post directly before your post. I had the same problem. I couldn‘t find another solution than that, but it works. If you use your nas for business purposes, it may not be a solution to do that, because you have to shutdown the server twice. But I am not a developer, maybe there is something that can be rewritten/changed at the plugin or maybe there is something else that can be done...

By the way, I didn’t recognize that the main issue of this thread was solved with the new omv-zfs plugin version 4.0.3.

@Blabla Read my post directly before your post. I had the same problem. I couldn‘t find another solution than that, but it works. If you use your nas for business purposes, it may not be a solution to do that, because you have to shutdown the server twice. But I am not a developer, maybe there is something that can be rewritten/changed at the plugin or maybe there is something else that can be done...

By the way, I didn’t recognize that the main issue of this thread was solved with the new omv-zfs plugin version 4.0.3.
Regards Hoppel

Thanks! it's not a big deal since I use it at home. If there will be a better solution for this weekend I will follow it, otherwise I'll go with you solution

I had to restart my Server and it happened again, i can't access my ZFS-Pool. It is mounted and I see it, but it's missing in the Drop-Down. Which combination of OMV, OMV-Extra, ZFS-Plug In and Kernel is working right now?

OMV 4 with the 4.0.4 zfs plugin and the proxmox kernel (no compiling needed, remove debian kernels too) seem very good on my test VM but I don't use it for important things. The version of omv-extras really doesn't matter as long as it has the proxmox kernel install button.

OMV 4 with the 4.0.4 zfs plugin and the proxmox kernel (no compiling needed, remove debian kernels too) seem very good on my test VM but I don't use it for important things. The version of omv-extras really doesn't matter as long as it has the proxmox kernel install button.

Briefly, what are some of advantages of using the proxmox kernel versus using the backports kernel?

The proxmox kernel is the Ubuntu 18 kernel (well tested and I am a fan of Ubuntu). It has zfs builtin and it is well tested against the stretch userland (since that is what proxmox uses). Plus, there is a repo for it which makes it easy to add to OMV.

By the way (and I know this is totally off topic but) talking of being a fan of Ubuntu: I have used Netplan recently for the first time in bionic... I really quite like it. Network manager can still go though

The proxmox kernel is the Ubuntu 18 kernel (well tested and I am a fan of Ubuntu). It has zfs builtin and it is well tested against the stretch userland (since that is what proxmox uses). Plus, there is a repo for it which makes it easy to add to OMV.

Please pardon me for extending this - but just one more question.

If using the proxmox kernel with OMV4 (VIA OMV-extras):
Based on the above, I'll take it that the kernel headers for ZFS are already installed. Will OMV's ZFS plugin install and work properly?

What I'd like to know is how they are managing to get away with that... I thought the Ubuntu installations just matched the Kernel with the ZFS files in the main repo... ergo, it 'comes' with ZFS after a single apt. They always make sure everything matches etc - so a simple install procedure. But what this seems to suggest with the Proxmox kernel is that ZFS is being bundled with a GPLv2 project... or am I mistaken? Kudos to them if it is.... I'm starting to think the reason Oracle aren't changing the license is because they don't have permission of all coders - but they don't actually care. They won't do it, because that would be seen as a really bad example, but they couldn't care less (or even applaud?) those who do? Who knows.... why haven't they taken legal action if there are these 'breaches'?

Oh and while we are on the subject of dear old Oracle.... I'm gonna make some enemies here... Oracle Linux is better than Centos. Yep.. I said it. I have changed my opinion. Why? Upstream delay is a LOT less and they use an Ubuntu style 'pay if you want'. I'd normally steer clear of anything Oracle, but if you want RPM that's binary compatible to Redhat (but not) then OEL wins. *runs and hides*

Edit: This is not to say that I think Red Hat (and derivatives) are better than Debian (and derivatives). Just that if I were forced to use a Red Hat distro with a zero budget that it wouldn't be Centos.

ut what this seems to suggest with the Proxmox kernel is that ZFS is being bundled with a GPLv2 project... or am I mistaken?

The zfs kernel module is included in the kernel package. My understanding from reading Canonical postings is that this is legal since it is not compiled into the kernel itself. I think including the package without downloading it is the gray area but Canonical's lawyers must think it is ok.

This is not to say that I think Red Hat (and derivatives) are better than Debian (and derivatives). Just that if I were forced to use a Red Hat distro with a zero budget that it wouldn't be Centos.

I am forced to use RHEL and CentOS (and a few installs of Oracle as well). Their support is terrible even if you pay for it. Canonical's is quite good. I would love to never use an rpm-based distro again

Really? I misread that because I think I wanted to assume you were talking about Oracle.. I thought the almighty Red Hat would win on this... after all, the support they sell is basically their business. You’d think they’d want to shine above the likes of Oracle. If review sites are anything to be believed, they seem to put Oracle in favourable light.